1. Field of the Invention
The present invention relates to a thread ring gauge and, more particularly, to a thread ring gauge including a measuring hole having a reducible inner diameter.
2. Description of the Related Art
Conventional thread ring gauges include a measuring hole having an inner threading and an inner diameter for measuring sizes of screws or bolts. In one type of thread ring gauges, the inner diameter of the measuring hole is fixed such that the thread ring gauges can not be utilized after the inner threading is worn out and, thus, causes a change in the inner diameter. In another type of thread ring gauges, the inner diameter of the measuring hole is adjustable. In an example disclosed in U.S. Pat. No. 1,447,448, the female gauge includes a gauge body having a split formed between two relatively adjustable end sections. The female gauge includes an interior gauge surface adapted to contact with parts to be gauged. Two aligned screws are mounted in aligned apertures in the end sections. One or both of the screws can be rotated to adjust the split.
In use, the inner diameter of the interior gauge surface of the female gauge is calibrated to be equal to a nominal size, and the split is filled with wax to indicate that the female gauge is of the nominal size. The wax cracks when the inner threading becomes worn. In this case, the wax cracks, and the female gauge must be recalibrated to the nominal size. However, the wax could crack due to other reasons including, but not limited to, impact to the female gauge or a change in temperature. Recalibration is troublesome, for the precision tolerance is only about 8μ.
Thus, a need exists for a thread ring gauge that can be easily calibrated while having a longer service life to reduce costs.